Some issues regarding jcmd <pid> JavaThread.dump

[Alan Bateman]

On 12/05/2021 01:33, Wenting Tan wrote:
> Hi,
>
> When I try to use jcmd <pid> JavaThread.dump with a small test program (VirtualThreadTest.java), there are two issues with virtual thread dump (jcmd_JavaThread_dump.txt).
>
>    1.  Virtual threads are running with busy loop, and jcmd process is stuck. After I force stop the processes, thread dump for some virtual threads are not captured. In my case, 10 virtual threads are created, and my Mac has 8 virtual cores, so 2 virtual threads are not captured. Not sure if this behavior is expected.
Thanks, there's enough here to see that there is a bug with the async 
stack trace for virtual threads that have been scheduled to start but 
never get to run because all carrier threads are busy.

>    2.  When lambda instead of method reference is used, the line number is not correct in the stack traces for those virtual threads. Note the three lines in the dump: VirtualThreadTest.lambda$main$0(VirtualThreadTest.java:26).
This may not be a loom issue. Can you send something here that shows the 
issue? I can't tell if this is a javac issue or something else.

-Alan